Welding machine and procedure for welding attachments to base members and having provision for inhibiting welding when the base members are misoriented



Feb. 11, 1969 c. w. GARVER ETAL 3,427,425

WELDING MACHINE AND PROCEDURE FUR WELDING ATTACHMENTS TOBASE MEMBERS ANDHAVING PROVISION FOR INHIBITING WELDING WHEN THE BASE MEMBERS AREMISORIENTED .Qriginal Filed March 15, 1962 Sheet 1 or 9 Feb. 11, 1969 O.W. GARVER ET AL WELDING MACHINE AND PROCEDURE FOR WELDING ATTACHMENTS TOBASE MEMBERS AND HAVING PROVISION FOR INHIBITING WELDING WHEN THE BASEMEMBERS ARE MISORIENTED Original Filed March .15, 1962 Shea t g of '9 mOscar WGczrvek KredI/LQK 5. U) )mqm Christian, @l.=stettrr Q-lavws@JiQdopP 3,427,426 mmn'rs TO BASE I Feb. 11, 1969 O. W. GARVER ET ALWELDING MACHINE AND PROCEDURE WELDING AT'IAC MEMBERS AND HAVINGPROVISION FOR INHIBITING WELDING WHEN THE BASE MEMBERS ARE MISORIENTED'Original Filed March 15, 1962 Shet 3 M9 1 l 1 I I l t t l I 1 I l l Y 1l 1 v 1 v 1 1 1 v 1| Feb. 11, 1969 o. W GARVER E 3,427,425 WELDINGMACHINE AND PROCEDURE FOR WELDING ATTACHMENTS T0 BASE MEMBERS AND HAVINGPROVISION FOR INHIBITING WELDING WHEN THE BASE MEMBERS ARE MISORIENTEDOriginal Filed March 15. 1962 Sheet 4 of 9 bjdugqf 01, 1436 M...

Feb. 11, 1969 o. w. GARVER E 3,427,425

WELDING MACHINE AND PROCEDURE FORWELDING' ATTACHMENTS To BASE MEMBERSAND HAVING PROVISION FOR INHIBITING WELDING WHEN I v THE BASE MEMBERSARE MISQRIENTED Original Filed March 15. 1962 Sheet wvnflawom 24/?Carver Imam fiieltler 0 a-v'romcvf Qecierick lqll Feb. 11, 1969 o. w.GARVER ETAL.

3,42 7,426 ND PROCEDURE FOR WELDING ATTACHMENTS; TO BASE MEMBERS ANDHAVING PROVISION FOR INHIBITING W ELDING WHEN WELDING MACHINE A THE BASEmszmamns ARE msoaxmrnn Original Filed March 15. 1962 Sheet Q NW \M'HM IOJcar h/7'61: r've ck. 6:. qlllmam an; by: WM,

Original File March 15, 1962 Feb. 11, 1969 o. w. GARVER E AL 3 WELDINGMACHINE AND PROCEDURE FOR WELDING ATTACHMENTS TO BASE MEMBERS AND HAVINGPRQVISION FOR INHIBITUG WELDING WHEN THE BASE MEMBERS ARE MISQHIENTEDSheet L or 9 d v e r 4 329? 366, 402.. O,

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- WELDING MACHINE AND PRQCEDURE FOR WELDING ATTACHMENTS TO BASE MEMBERSAND HAVING PROVISION FOR INHIBITING WELDING WHEN THE BASE MEMBERS-AREMISORIENTED Original- Filed March 15, 1962 Sheet 8 'or '9 r, COUNTER swI 553 90 5 N MAW MOTOR 54 ORIENT DRIVE Has?- w 'MOTO R S (2) COARSE 02mmCLUTCH I EAR moP 1 RELOAD L J W314i; 534 EN? DROP RELEASE 455 '45:; aw,7 6 w 0 5,35 CONTELLER 5% 7 580 v EAR TEST 585 59 IIJ 31 480 '480 COU rZERO RESET COUNTER v if F 4 ADJUSTMENT MOTOR DOWN I J 2 5:0

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. reb. 1 1, 1969 o. w. GARVER ET 3,427,425

WELDING MACHINE AND PROCEDURE FOR WELDING ATTACHMENTS T0 BASE MEMBERSAND HAVING PROVISION FOR INHIBITING WELDING WHEN 1 N THE BASE MEMBERSARE MISORIENTED Original Filed March 15. 1962 Sheet 9 or 9 5 4 M E -G 6a zg zz Projedi'now he Lghf F2 F3 FORCE CR wwcraMBY/ United StatesPatent Oifice 3,427,426 Patented Feb. 11, 1969 Application Apr. 29,1965, Ser. No. 463,062, now Patent No. 3,368,056, dated Feb. 6, 1968,which is a division of application Ser. No. 180,415, Mar. 15, 1962, nowPatent No. 3,233,072, dated Feb. 1, 1966. Divided and this applicationDec. 1, 1967, Ser. No. 687,350 US. Cl. 219-80 8 Claims Int. Cl. B23k9/12, 11/10, 11/02 ABSTRACT OF THE DISCLOSURE A welding machine andprocedure for welding attachments to base members on a high speedproduction basis and wherein provision is made for detecting theposition of the base members and for feeding one or more of theattachments relative to each base member only when the latter are in apreselected oriented position, thereby precluding the welding ofattachments to misoriented base members.

Cross reference to related applications The present application is adivisional application based on the copending application of Oscar W.Garver, Frederick E. Ullman, Christian Hv Stettler and Hans W.

Kopp, Ser. No. 463,062, filed Apr. 29, 1965, now Patent No. 3,368,056;such copending application having been a divisional application basedupon the then copending application of the same inventors, Ser. No.180,415, filed Mar. 15, 1962, and issued as US. Patent No. 3,233,072 ofFeb. 1, 1966; all assigned to the assignee of the present invention.

Background of the invention The present invention relates to weldingmachines and procedures, and, more particularly, to machines andprocedures for welding attachments to base members. In its principalaspects the present invention is concerned with improved weldingapparatus having provision for feeding the attachments relative toprecisely oriented members and for precluding feeding of attachmentsand, therefore, for precluding welding, whenever the presence of amisoriented base member is detected. While not so limited in itsapplication, the attachments may conveniently take the form. of ears andthe base members may conveniently take the form of pails.

In the manufacture of metal shipping pails, it is conventional to weldears or projections to the sides of the pail for receiving the ends of awire bail. The ear may be in the form of a cup shaped stamping having acentral opening for the bail and having lateral projections which seatagainst the side of the pail. Since the pails are commonly made of sheetsteel, it is desirable to protect or decorate the outer surface eitherby painting or by lithographing which, in addition to providing physicalprotection, often serves to identify the contents, to provide acolorful, attractive appearance, and to carry an advertising message. Itis desirable that the painted or lithographed coating be applied to theside of the pail while it is still flat, prior to welding. Moreover, itis desirable that the coating be continuous, covering all of the surfacearea. This requires that the bail ears be secured after the coating hasbeen applied, so that any spot welding of the ears must take placethrough the coating. Efforts have been made in the past to weld an earor other attachment to a painted surface by forming, on the attachment,a sharp projection so that when pressure is applied, the projectionestablishes electrical contact to permit flow of welding current.However, it has not been possible to weld through an insulating coatingwith one hundred percent reliability. Consequently, use of thisprocedure has been limited to containers having thin walls and where thestrength of the weld has not been an important factor, for example, inthe welding of a key to the lid of a coffee can. One difficulty whichhas been experienced in this type of welding is the flashing which takesplace when the initial electrical contact is made between the sharpprojection and the base resulting in overheating and destruction of theprojection, with inability to complete the weld.

Welding through an insulating coating has been avoided in the case ofshipping pails because of inability to make a consistent weld, becauseof the high degree of strength required in the weld, particularly whenthe pail is to be filled with a dense, heavy substance, and theinability to properly inspect the weld for soundness.

It is an object of the present invention to provide a welding machineand procedure which are not only capable of producing a reliable weldbut which are extremely rapid, a single machine being capable ofprocessing shipping pails at the rate of 2400 units per hour or evenhigher. It is a more specific object in this connection to provide anautomatic machine in which the positioning and welding procedure isperformed in steps at successive work stations, with the pail or similarbase member being indexed from station to station and with a pluralityof base members being acted upon simultaneously in the successivestations.

It is still another object of the present invention to provide a weldingmachine and procedure wherein provision is made for consistently andaccurately positioning the base members so that a seam or otherdiscontinuity therein is precisely located, and for feeding ears orother attachments thereto prior to a welding operation and only when thebase members are in their precisely oriented position, thus precludingthe welding of attachments to misoriented base members. It is a moredetailed object to provide means for insuring positive positioning whichdetermines whether the position of the pail is within predeterminedtolerance and which includes provision for preventing a weld by failureto provide an ear if the tolerance is exceeded.

In a more detailed aspect of the invention, it is an object of theinvention to provide a novel orienting and feeding apparatus for thebail ears which is capable of feeding them one-by-one down a feed chuteby means 0' an escapement mechanism timed with the movement of thewelding guns and the indexing of the pails from station to station inthe machine, yet wherein operation of the escapement mechanism isinhibited whenever the pails are improperly oriented so as to precludeear feed and, therefore, to preclude welding of ears to misorientedpails.

It is yet another object to provide a machine of the above type which iswell suited for heavy industrial use, which may be operated for longperiods of time without maintenance or adjustment and which issubstantially foolproof, permitting safe operation on a high productionbasis even with unskilled or inexperienced personnel,

Other objects and advantages of the invention will become apparent uponreading the attached detailed description and upon reference to thedrawings, in which:

FIGURE 1 shows a shipping pail with a bail ear afiixed by the presentmachine;

FIG. 1a is an enlarged perspective showing one of the ears;

FIG. 2 is a front elevation of an ear welding machine constructed inaccordance with the present invention somewhat simplified for easyunderstanding;

FIG. 3 is a left-hand elevation of the machine shown in FIG. 2;

FIG. 4 is a diagram showing the linkage for driving the positioningmembers;

FIG. 5 is a fragmentary front view of the machine showing the cams fordriving the transfer and positioning members;

FIG. 6 is a fragmentary perspective showing the ear escapement;

FIG. 7 is a fragmentary section taken along the line 7-7 in FIG. 6;

FIG. 8 is a fragmentary face view in partial section showing the pailorienting mechanism;

FIG. 9 is a fragmentary section taken along line 9-9 in FIG. 8 showingthe first seam detector;

FIG. 10 is a fragmentary section taken along the line 10-10 in FIG. 8showing the seam detector switch;

FIG. 11 is a fragmentary top view of the star wheel employed in thefirst seam detector;

FIG. 12 is a fragmentary section taken along the line 12-12 in FIG. 8and showing the final seam detecting element;

FIG. 13 is a section taken along the line 13-13 in FIG. 2 showing themeans for moving the welding electrodes;

FIG. 14 is a fragmentary section taken along the line 14-14 in FIG. 13showing the electrode advancing means in plan view;

FIG. 15 is a fragmentary section taken along the line 15-15 in FIG. 13showing the electrodes in welding position;

FIG. 16 is an enlarged fragment showing the function of the centeringpin and suporting table;

FIG. 17 is a vertical section taken along line 17-17 in FIG. 14 showingthe opening of the gates to admit the welding electrodes;

FIG. 18 is a perspective of one of the gates;

FIG. 19 is a section taken on the line 19-19 of FIG. 2 showing the earchecking arm;

FIG. 20 is a view similar to FIG. 19 with the parts in a moved position;

FIG. 21 is a simplified schematic diagram of the control circuit;

FIG. 21a is a simplified graphic representation of the ON time for thecam switch sections shown in FIG. 21;

FIG. 22 is a plot showing the variation in applied force projectionheight and current as a function of time; and

FIGS. 2'3a23e are enlarged sections of a typical weld at successivepoints in the welding cycle keyed to FIG. 22.

While the invention has been described in connection with a preferredembodiment, it will be understood that we do not intend to limit theinvention to the embodiment shown but intend, on the contrary, to coverthe various alternatives and equivalent constructions included withinthe spirit and scope of the appended claims.

Turning now to FIG. 1 there is shown, inverted, a shipping pail ofwell-known type having a top curl 31, a bottom flange 32 and a seam 33.Located on opposite sides of the pail are bail ears 34, only one ofwhich is visible in the figure. The machine to be described is primarilyintended for welding such ears in place upon a prepainted orprelithographed pail, although those skilled in the art will appreciatethat it is not limited thereto. While the invention is not limited toany particular form of bail ear, a preferred form of ear (FIG. 1a)includes a cup-shaped central portion 35 having a central opening 36 forreceiving the end of the bail and having tabs 37, 38 for spot welding tothe Wall of the pail.

The machine, generally indicated at 50,

has a longitudinal frame 51 supported on a base 52. Extending upwardlyat the rear of the frame are pillars 53, 54 which support asuperstructure 55 in adjusted vertical position. Pails 30 enter themachine at the left from an external conveyor and, as will be described,each pail successively occupies a series of work stations in which thepails are acted upon. In the machine described, there are a total of sixwork stations indicated at 61-66, respectively, in which the pails arefirst oriented, then welded and, finally, tested. For the sake ofversatility and for optional functions or specialized purposes, two ofthe stations, in the present instance stations 63 and 66, are idle. Itwill be understood, however, that the pails pass through the machine atclosely spaced sequence so that all the stations at any given time havepails positioned therein. While the various functions performed by themachine are closely integrated, it will, nevertheless, be convenient foreasy understanding to discuss the functions of the machine underseparate appropriate subheadings.

Pail transfer and positioning mechanism In carrying out the presentinvention a longitudinal pail transfer member is provided which extendsunder all of the stations and which reciprocates back and forth througha unit station-to-station distance for the purpose of engaging thedownwardly presented facing edges of the pails and for moving all ofthem simultaneously to the next station. Cooperating with the transfermember is a longitudinally extending positioning member having means formoving the same vertically between a lowered inactive position, at whichtime the pails are engaged by the transfer member, and an upraisedactive position in which the pails are firmly held clear of the transfermember so that the latter is free to make a return stroke. The transfermember in the present instance is in the form of a longitudinallyextending bar 70 mounted on rollers 73, 74 (FIG. 19) for endwisemovement in the machine and having a plurality of pail-engaging membersor lugs 71-72 secured to its upper edge. A pair of cams are employed formoving the transfer member in opposite directions. Thus, as shown inFIG. 5, drive cams indicated at 81, 82, mounted on a cam shaft 83 actupon a bell crank 84 which is pivoted for rocking movement about a shaft85. At its upper end of the crank is connected to a link 86 which, inturn, is pivoted to a bracket 87 clamped to the transfer member 70. Forthe purpose of driving the cam shaft 83, a motor 90 is used having aspeed reduction unit 91.

For the purpose of moving the pails upwardly and clear of the transfermember 70 into a position to be acted upon, a positioning member 160 isprovided having spaced sections 101, 102 which move upwardly anddownwardly in unison. The positioning member is formed in twolongitudinal sections in order to permit separate vertical positioningof the pail in the welding station as will be discussed in detail.

In order to provide a wide base for positioning purposes, the sections101, 162 have corresponding spaced sections 101a, 101b, 102a and 102])which straddle the transfer member 70 as shown in FIG. 3. Means areprovided along the top edge of each section for engaging the lower edgeof the pails. Such means may take the form of lugs 105 or may take theform of rollers in the orienting stations 61, 62 to be discussed. Tounderstand the means for bodily raising and lowering the positioningmember 100, it will be noted that cams 111, 112, mounted on shaft 83 anddisposed immediately behind the cams 81 and 82 previously discussed, actupon a cam follower in the form of a bell crank 114 having a shaft 115.Connected to the outer end of the bell chank 114 is a push rod 115 whichis pinned to an arm 117 secured to a longitudinally extending rockershaft 120 which is journaled at its end in suitable bearings 121. Toconvert the rocking movement of the rocker shaft 120 to verticalmovement of the positioning member, the shaft is provided with lift armsalong its length having short links which are coupled to the sections ofthe positioning member and with radius arms being provided to insurethat the elevation is equalized. Thus the shaft 120 has lift arms 125carrying short links 126 which are connected at their upper ends tobrackets 127 on the section 102a. For the purpose of transmitting equalmovement to the section 102b, the bell crank shaft 115 has an arm 114awhich drives a push rod 116a pinned to an arm 117a on a rocker shaft120a which extends along the rear of the machine. The rocker shaft 120acorresponds to the rocker shaft 120 previously discussed. To elevatesection 102b the pushing member of the rocker shaft 120a has arms 125awhich act upon short links 126a which are connected at their upper endsto brackets 127a along the underside of the member 1021).

It will be apparent, then, that when the cams rotate the members 102aand 102b will be moved upwardly through equal distances. To insure thatthe members are guided in this upward movement, pairs of swingableradius arms 129 are provided for each of the sections, forming aparallelogram linkage.

While the above structure suffices for elevating the sections 102a, ofthe positioning member 100, it will be understood that similar structureis employed for elevating the two sections 101a, 101k and withcorresponding reference numerals being used where applicable.

Since cams 81, 92 which reciprocate the transfer member and the cams111, 112 which move the positioning member 100 vertically are offset inphase, it will be seen from FIG 3 that the effect is to advance thepails simultaneously step by step. Taking the first station 61 by way ofexample, when the positioning member 100 is upraised, the lugs on thetransfer member are moved to the left to a position under the enteringpail. When such entering pail, indicated at 30a in FIG. 2, is lowered bythe positioning member, it seats on the lugs 71 and 72. The transfermember 70 then moves to the right until the pail is in the first station61 whereupon the transfer member momentarily comes to rest. Thepositioning member 100, as a result of the cams 111, 112 and the linkagejust described, moves vertically, lifting the pail clear of the transfermember and in position to be acted upon in the first station. Each ofthe other pails in the series is similarly advanced one step.

In order to feed a pail into the machine and to remove a pail havingwelded ears from the machine, conveyor chains are provided at both theinput and output. Referring to the input end, a conveyor chain 140,which preferably consists of two parallel sections is trained aboutshafts 141, 142, the shaft 142 being preferably mounted on thepositioning member 100 for movement up and down therewith. For drivingthe conveyor chain 140', a drive chain 143 is provided which is drivenby a second chain 144 coupled to the driving motor. A similar setup isemployed at the output, with a conveyor chain 150 being trained aboutshafts 151, 152 and driven by chains 153, 154.

Rotary orienting mechanism In the exemplary apparatus, and as disclosedand claimed in our aforesaid copending application Ser. No. 463,062,filed Apr. 29, 1965, provision is made at the first station 61 forrotating the pail at relatively high speed to an approximate position oforientation as determined by a weld bead on the side of the pail .and atthe second station for rotating the pail at a substantially slower speedto achieve precise orientation. In order to understand the mechanism foraccomplishing such two-step orientation, reference is made to FIGS. 2and 8-11 and the schematic control diagram FIG. 21. Mounted on thesuperstructure 55 and centered with respect to the stations 61, 62 arerotating mechanisms 161, 162. Attention will first be given to therotating mechanism 161. The mechanism 161 is mounted upon a downwardlyextending pedestal 163 carrying a cylindrical housing 164 at its lowerend. The housing 161 has an outer shell for an adjusting purpose whichwill become clear as the discussion proceeds. Centered within thepedestal 163 is an input drive shaft 165, and projecting downwardlytherefrom is a disc drive shaft 166. Coupled to the lower end of thedisc drive shaft 166 is .a drive disc 170 having a layer of rubber orother friction material 171 on its under surface for engaging thepresented upper edge of a pail 30. Downward pressure is exerted upon thedisc 170 so that the disc seats firmly against the pail by means of aresilient connection 172 which is interposed between the drive shaft 166and the disc. The resilient connection 172 is preferably in the form ofa resilient spider, a construction well-known to those skilled in theart.

For the purpose of controlling rotation of the disc, a clutch 175 isinterposed between the input shaft 165 and the output shaft 166 and, tobring the output shaft to a stop on the plate when the clutch isdisengaged, an electric brake 176 is provided. The combined clutch andbrake together form a commercially available unit. To supply rotativepower for the input shaft 165, to rotate the same at a speed ofapproximately 50 r.p.rn., a reduction drive is provided which includes adrive motor 180, a rightangled step-down connection 131 having adownwardly extending output shaft 182. Mounted on the shaft 182 is aspur gear 183 which meshes with a spur gear 184 at the upper end of theshaft 165. In order to permit rotation of the pail under the urging ofthe drive disc 17 0, rollers 185, which may be made of nylon or thelike, are mounted along the upper edge of the positioning member 100.

In order to detect the arrival of the pail seam at a pre determinedpoint, and to deenergize the clutch and energize the brake when thisoccurs, a detector is provided in the form of a sharp edged member whichis biased against the side of the pail and which operates an associatedswitch when the sharp edge is engaged by the seam. Turning to FIGS. 10and 11 the detector element is in the form of a star wheel mounted upona shaft 191 carrying a cam 192 at its upper end for operating a switch193, The shaft, as shown in FIG. 9, is mounted in a carrier 195. Forbiasing the carrier in the direction of the pail, the carrier is mountedupon a lever 196 which is pivoted at its upper end 197 and which isengaged by a coil spring 198. Thus while the pail rotates, the starwheel 190 presents an edge 190a in the path of movement of the seam 33on the pail. It will be understood by one skilled in the art that evenwhere a flush-type seam is employed, nevertheless, there is a narrowrather sharply defined groove on the surface of the pail capable of engagement by the star wheel. When the seam rotates to the position shownin FIG. 11, the point 190a of the star wheel enters the seam groovecausing the star wheel to step one step in the counterclockwisedirection. The cam 192 at the upper end of the star wheel shaftthereupon actuates the switch 193 which, through the control circuit tobe described, serves to disengage the clutch and energize the brake tobring the pail to a stop.

Means are provided for retracting the seam detector to an upper,out-of-the-way position during station to station transfer and forlowering the detector when a pail is in the orienting station. Tounderstand the retracting means reference is made to FIGS. 3, 8 and 9.It will be noted that the detector assembly is not rigidly secured tothe housing of the rotating mechanism, but, instead, is mounted upon avertical slide 210 which engages way surfaces 211 secured to the housingmember outside of the housing 161. For moving the slide 210 upwardly anddownwardly, a positioning collar 215 is provided which surrounds thepedestal 163 and which is slidable thereon. Formed in the lower portionof the collar 215 is an annular groove 216 which is engaged by a roller217 pinned to the slide 210. Thus, it will be apparent that when thecollar is raised, the slide 210, and the detector assembly secured toit, is also raised, this condition being illustrated in FIG. 9. For thepurpose of moving the collar 215 upwardly during each transfer cycle, alinkage is provided which is operated by the rocker shaft 120. Suchlinkage includes an arm 220 (FIG. 3) which is connected to a push rod221 operating a bell crank 222. Motion is transmitted from the bellcrank 222 to a second or intermediate bell crank 223 by a parallelogramlinkage made up of links 224, 225. Motion is transmitted from the bellcrank 223 to a final bell crank 226 which is rotatable about a shaft 227via a second parallelogram linkage made up of parallel links 228, 229.For the purpose of transmitting the rocking movement of the shaft 227 tothe collar 215, arms 231, 232 (FIG. 8) are secured to the shaft carryingrollers 233, 234 at their forward ends which ride in an annular groove235 at the upper end of the collar,

Provision is also made for camming the detector radially outward awayfrom the pail as it is upraised for the purpose of clearing the flangeat the end of the pail and the drive disc which engages it. In FIG. 9 itwill be noted that the spring biased arm 196 which carries the detecto-relement has a roller 240 which rides on the surface of the way 211 andacts as a cam follower. Thus, when the detector is drawn upwardly, theroller 240 rides up on the way swinging the detector outwardly.Conversely, when the collar 215 is lowered the roller 240 reaches thelower end of the way 211 providing dropolf so that the spring 198 iseffective to bias the detector element against the side of the pail.

It will be apparent, then, that upon rotation of the rocker shaft 120 inone direction the detector will be moved downwardly and inwardly intocontact with the pail and, upon movement in the other direction, i.e.,during transfer, the detector will be moved outwardly and upwardly to anout-of-the-way position. Because of the dual parallelogram linkage justdescribed, it is possible to adjust the height of the superstructure 55to accommodate pails of different heights, without necessity forreadjusting the angling of the collar-actuating arms 231, 232. Thesuperstructure adjusting means will be covered at a later point.

For the purpose of limiting maximum rotation of the pail to less than180, it will be understood that a duplicate of assembly 190 having aswitch 244 is provided in a diametrically opposite position (see FIG.3). As will be observed in the control diagram FIG. 21, operation of theswitch in either of the detector assemblies sufilces to terminaterotation of the pail. Stopping the pail at either of two 180 positionsis permissible since the ears to be welded to the pail are fixed insymmetrical 180 positions. For the purpose of simultaneously positioningthe detector assemblies 190, 190a, the associated way elements aresecured to an outer shell 245 of the orienting drive housing 161. Amanually operated clamping screw 246 serves to clamp the outer shell 245and the two detector assemblies in any position depending upon thedesired position of the bail ears.

The net effect of the orienting mechanism in the first station 61 is toproduce approximate orientation of the pail, say, within one quarterinch of the desired position on the periphery. Such orientation isapproximate because of the relatively high speed of rotation of thedrive disc 170 required to bring about a rotation of up to 180 in theshort time that the pail is in the station. The degree of overtravelafter cutoff is to some extent dependent upon whether the pail has beenrotated to a large angle or a small angle prior to cut off.

In the illustrative apparatus, means rotating at a substantially slowerspeed are provided in the second station in order to achieve final andexact positioning. Since the orienting mechanism employed in the secondstation is a substantial duplicate of that in the first, except for thespeed of rotation and the construction of the detector element,corresponding reference numerals have been employed to identifycor-responding parts with addition of subscript a. To achieve a slowerspeed, on the order of 6 rpm, a step-down ratio has been employed in thegears 183a, 184a, as contrasted with the step-up ratio in the gears 183,184 in the companion unit. With regard to the construction of the slowspeed detector, the element, indicated at 250 in FIG. 12, has a sharpdetecting edge 251 and is mounted upon a parallelogram linkage whichincludes links 252, 253. The link 253 is connected to a verticallyextending shaft 254 which controls switches 255, 256. The switch 255 isso adjusted as to operate immediately upon the sharp edge 251 beingengaged by the seam whereas the switch 256 is adjusted to operate onlyafter a predetermined amount of overtravel. The effective spacingbetween the switches 255, 256 deter mines the positional tolerance,i.e., as long as the orientation is within prescribed limits, an earwill be welded to the pail. However, and as covered in the latersection, in the event that the switch 256 is operated, indicating thatthe tolerance is exceeded, provision is made for preventing a weld sothat the pail may be removed from the production line and inserted againat the input side of the machine. Moreover, means are provided forregistering the number of successive pails which are outside of thetolerance, i.e., Without ears, and for sounding an alarm or shutting offthe machine when a predetermined number has been exceeded, all as latercovered in detail. Using the above construction, with approximate andexact orientation in successive stations, orientation may be achievedwithin a peripheral tolerance on the order of 0.080 inch consistentlyand at high speed. Upon subsequent lowering of the pail by thepositioning member, the pail is advanced into the next station 63. Thisstation, in the present construction, is an idle one in that nooperation is performed upon the pail. However, this station contributesto the versatility of the machine in that any desired operation,requiring an oriented pail, may be performed at this point. For thepurpose of bolding the pail securely in station 63 when it is upraisedby the positioning member, a stationary disc 260 is provided mountedupon a plunger 261 which is telescoped into a bushing 262. A coil spring263 interposed between the bushing and the disc biases the discdownwardly.

Positioning of pail in welding station and feeding of cars relativethereto in accordance with the present invention Means are providedwithin the welding station 64 for accurately positioning bail ears onopposite sides of the oriented pail in position to be acted upon by thewelding guns. Prior to describing the ear positioner, consideration maybe given to the means employed for positioning the pail at a properheight. It is one of the features of the illustrative welding machinethat a separate adjustable positioner is provided in the welding stationto enable variation in the height of the ear on the pail and asnecessary to avoid reinforcing beads which may be formed in the wall ofthe pail. Thus, there is provided, as shown in FIG. 5, a verticalpositioning member 280 which is mounted for vertical movement onvertical ways 281, 282.

A linkage connects the positioning member 280 to the rocker shaft 120 sothat the movement is coordinated and timed with the movement of thetransfer member 70 and positioning member previously discussed. Thislinkage in the present instance includes an arm 283 which is secured tothe rocker shaft and which is connected to a bell crank 284 having apivot point 285. A second bell crank 286 has a pivot point 287. Meansare provided for varying the effective point of connection between thebell cranks 284, 286. In the present instance this is accomplished byproviding a pivot block 288 in the bell crank 286 with an adjustingscrew 289 for adjusting the throw. It will be apparent that theadjustment 289 enables the positioning member 280 to reach any desiredheight at the top of the stroke at which point the ears are affixed.

For the purpose of holding the drum in position in the welding station,a disc 290 is mounted upon a shaft 291 slidable in the bushing 292, withthe disc being urged downwardly by means of coil spring 293 surroundingthe shaft.

Attention will next be given means for depositing an car on each side ofthe pail timed with the advancement of a pail into the welding station.For the purpose of orienting the ears to face the pail, an orientingdevice 300 (FIGS. 2 and 3) is employed having downwardly extendingchutes 301, 302 respectively. The orienting device does not per se form.a part of the present invention and it will be understood that anysuitable orienting arrangement, taken from the prior art, may beemployed. Moreover, it will be understod that conveyor means, forexample, of the magnetic belt type, may be provided for elevating thecars from a bulk source to the orienting device 300. Since the feedingarrangement-s for the two sides of the pail are identical, attention maybe focused upon that visible at the front of the machine as bestillustrated in FIGS. 6 and 7.

In accordance with the present invention, provision is made for feedingears to positions adjacent precisely oriented pails one at a time inseriatim order, yet for precluding the feeding of cars whenever amisoriented pail is detected. To this end, an escapement 310 is providedat the lower end of the chute 301. The escapement includes a rockingassembly 311 which is oscillated about a pivot 312 by means of a link313 which is connected to solenoid operators having input coils 314,314a. For the purpose of accepting an car from the chute 301 at one endof the stroke and for releasing the car at the other end of the stroke,the escapement member 311 includes a flat leaf spring member 317 havinga retaining forward edge 318 mounting a cam follower 319 whichcooperates with a stationary cam surface 320. It will be apparent thatwith an ear in the position shown in FIG. 6, clockwise rotation of theescapement will cause the cam follower 319 to approach the cam 320. Whenengagement takes place, the cam follower is cammed laterally, bendingthe leaf spring 317 so that the edge 318 thereof moves out of the way ofthe ear, whereupon the ear is permitted to fall through a final verticalslide chute 321. Preferably, the sides of the chute 321 are grooved asindicated at 322 so that the ear is positively guided in its downwardmovement. The escapement member includes an obstructing face indicatedat 325 which holds the next succeeding ear, indicated by the dot-dashoutline, in the position shown until the escapemcnt member has fullyretracted, whereupon such ear drops into place in readiness for asubsequent discharge cycle. Control circuits for energizing the coils314, 31411 of the solenoid will be discussed in detail in connectionwith consideration of FIG. 21. It will sufiice for the present to saythat reload of the escapement is disabled whenever the pail is not inproper orientation, i.e., whenever the switch 256 is actuated indicatingthat the positional tolerance has been exceeded.

Referring next to FIGS. 13-17 conjointly, means defining a supportingtable are provided for catching the ear as it descends down the finalchute 321 and for supporting the car at the proper height in horizontalposition. Moreover, means including a tapered positioning pin areprovided for entering the bail opening and for precise final centeringof the car just prior to engagement by the welding electrodes. Thus,there is provided at the welding station a locating table 330 and atapered centering pin 331 with means for bringing them into operationsequentially. Sequential operation is brought about by mounting both ofthe elements on a vertically arranged positioning arm 332 having anupper horizontal axis 333 and by providing a resilient mounting to holdthe table in projecting position. Thus, in the present instance thetable 330 has a mounting :block 334 which is slidable on a rearwardlyprojecting rod 335 and which is biased to a forward position by a spring336. Accordingly, as the centering arm 332 is swung forwardly, i.e., inthe direction of the pail, the table 330 first engages the wall of thepail to provide a positive stop for the advancing bail ear 34. Uponcontinued inward movement of the arm 332, the tapered centering pin 331enters central opening 36 in the car so that the ear centers itself withrespect to the pin. Since the pail is rotationally oriented with respectto the machine, and since the ear is thereby positioned with respect tothe machine while being held horizontal, it will be apparent thatprecise location of the car on the side of the pail is assured. Meansare provided for swinging the positioning arm timed with the movement ofthe welding guns as covered in the following section.

Construction and actuation of welding gzms In the welding station twoseparate welding gun assemblies 350 are provided, one at the front ofthe machine and one at the back, each consisting of two sets ofelectrodes so that both of the ears are welded simultaneously. Since thetwo assemblies are substantially identical, detailed attention may begiven to the assembly at the front of the machine. In the exemplarywelding system, the piece to be welded is provided with a sharpprojection at each point of welding for penetration of a protective, orinsulating coating on the pail, and means are provided for advancing thewelding electrodes by positive mechanical action to develop a forcesufficient to cause penetration of the coating by the projectionfollowed by substantial collapse of the projection before weldingcurrent is applied, thereby to produce a sound weld free of any tendencytoward flashing, or burning away, of the projections. To make the twowelds, the welding assembly 350 has two welding guns 351, 352. The firstgun 351 is mounted on a bracket 353 secured to a frame 354. The bracketis of C-shape having guide portions 355, 356. Mounted for slidingmovement in the bracket is a cylindrical electrode carrier 357 mountinga rod 358 which projects forwardly, carrying an electrode 359 having aterminal 360.

The second gun 352 is mounted in a bracket 363 having ends 365, 366 forthe slidabe mounting of a cylindrical electrode carrier 370* having arod 368 terminating in an electrode 369 and terminal 370a. The returncircuit for the electrodes 369, is completed through a relativelystationary electrode 371.

Means are provided in the present construction for cyclically retractingthe electrode 371 down wardly so that it is out of the way of a pailbeing advanced into the welding station and for then moving theelectrode upwardly to a position within the pail after the pail comes torest. In the present instance this is accomplished by mounting thereturn electrode 371 at the end of an electrode arm 375 which is pivotedto the base 354 upon a shaft 376. Extending downwardly from the arm 375is a drop link 376a which is connected to an arm 377 mounted on therocker shaft 120. It will be apparent that when the rocker shaft rocksduring the transfer portion of the cycle, the arm 375 and its electrode371 are swung downwardly clear of the advancing pail and swung upwardlyagain to the position shown when the lpail is clamped in the weldingstation.

Means including a stiff preloaded spring are provided for positivelyadvancing the welding electrodes and for maintaining the electrodesclamped securely against the ear prior to, and during, the weldingcycle. Thus, referring to FIG. 14, a spring 380 is mounted within thecylindrical carrier 357 surrounding the rod 358. The rod is formed withan enlargement 381 which is normally seated in a recess 382 formed inthe forward end of the cylinder. The spring is compressed at its rearend by a preload adjusting member 385 which is in the form of a bushingthreaded into the end of the cylinder 357, the bushing having a centralbore 386 for clearing the rod 358. It will be apparent, then, that whenthe bushing 385 is screwed into the end of the cylinder, the spring iscompressed to exert a substantial force, which in a practical case maybe on the order of 350 lbs. against the enlargement 381 on the rod.Thus, when the carrier cylinder 357 is advanced forwardly, and theelectrode strikes the workpiece, there is an immediate buildup of forceagainst the workpiece until the force is suflicient to lift the rod fromits seat 382 against the force exerted by the preloading spring. Aspring pressure of at least the value of the preload then continues tobe exerted against the workpiece during the remainder of the weldingcycle. It will be understood that an identical preloaded springarrangement is included within the cylinder 367 associated with thecompanion welding electrode.

For the purpose of advancing the electrode carriers with positivemechanical action for complete overcoming of inertial effects, ascontrasted with the non-positive action of an air cylinder or the like,a driving linkage is employed including a cam and over-driven calmfollower driven by the cam shaft 83-. Thus, there are mounted on theshaft 83 a pair of cams 391, 393 which cooperate with a cam followerlever 393a to reciprocate a vertical link 394. The latter drives a bellcrank 395 which is mounted for rocking about a shaft 396. The upwardlyextending portion 397 of the bell crank is pinned to the reciprocatingbar 398. For the purpose of insuring substantially pure reciprocation, asecond vertical link 399 is provided which is pivoted on the shaft 326and which serves to complete a parallelogram. In short, rotation of thecam shaft causes the bar 398 to reciprocate backwarclly and forwardly.For the purpose of coupling the. reciprocating bar to the electrodemounting cylinders, short links 401, 402 are provided in the form ofturnbuckles which are secured at their forward ends to the bar 398 andwhich are connected at their rear ends to clamps 403, 404 respectivelywhich grippingly encircle the two cylinders. The walls of the cylindersmay be grooved as necessary to accommodate or clear the rear ends of thelinks 401, 402.

In accordance with one of the detailed features of the presentconstruction, gates are provided at the lower end of the chute 321 forthe purpose of guiding an ear dropped by the escapement 3110, to weldingposition together with means for moving the gates out of the way of theadvancing electrodes 359, 369. Thus referring to FIGS. 17 and 18, twogates 411, 412 are provided having longitudinal grooves 413, 414 whichserve to guide the ends, or welding tabs, on the ear 34. The grooves413, 414, with the gates in normal position, are alined withcorresponding grooves in the chute 321. To mount the gates for outwardswinging movement they are pivoted upon pins 415, 416 respectively. Thegate 411 is held closed by a coil spring 421. The spring is mounted on apush rod 422 which is guided at its upper end at 423 and which ispinned, at its lower end, to an arm 424 on the gate. The normal orclosed position of the gate is defined by engagement of stop surfaces at425. A corresponding spring 431 on a rod 432 serves the same purpose forthe gate 412. In order to swing the gate apart a cam and cam followerare interposed between the gate and the centering arm 332 which carriesthe centering pin 331 previously discussed. Thus, there is provided onthe centering arm a transversely positioned cam plate 440 engaging camrollers 441, 442 mounted on the gates 411, 412 respectively.

Attention may next be given to the means employed for swinging thecentering arm 332 to insure that it is timed with respect to theadvancement of the electrodes. As shown best in FIG. 13, such arm iscoupled to the reciprocating bar 398 which serves to drive the electrodesupporting cylinders. Thus, connected to the bar 398 and extendingupwardly therefrom is a link 450 which is pivoted at its upper end 451on a frame bracket 452. For interconnecting the arm 332 and the link 450a push rod 453 is provided which is pinned to the arm at its forward end454. The connection is made resilient by coil spring 455 surrounding therod and which engages a slidable collar 456 pinned to the center of thelink 450. It will,

therefore, be apparent that when the bar 398 is moved fonwardly,pressure is exerted by the link 450 upon the spring 455 to move the pushrod 453 in the forward direction so that the pail is engaged by thetable, the ear is engaged by the centering pin and the gates are spreadapart just ahead of the advancing electrodes.

Switches 457, 458 actuated by a cam surface 459 at the forward end ofthe push rod are operated depending upon whether the push rod goes toofar or not far enough. The switch 458 thus signals the absence of an earin the welding position while the switch 457 signals improperpositioning, the welding guns being disabled in either event as will bediscussed in connection with the control circuitry.

Ear checking arrangement In the exemplary apparatus, feeler means areprovided for checking the presence of ears on the pail upon transfer ofthe pail from the Welding station. More specifically, feeler arms arepivoted to the frame in the checking station and moved inwardly towardthe pail to engage the ears when the pail is raised by the positioningmember 100. Referring to FIGS. 19 and 20, the feeler arm arrangement atthe front and rear sides of the machine is shown in detail and it willbe understood that the following description is applicable to both.Thus, the arm 470 is pivoted at 471 to the frame of the machine. At itsupper end the arm carries a pivoted finger 472 having an ear engagingtip 473. For the purpose of adjusting the vertical position of thefeeler member, the arm has two relatively slidable portions including acarrier 474 and with the relative position being adjustable by a controlknob 475 which engages a nut 476 on the carrier. For the purpose ofbiasing the feeler member 472, a spring is provided, with the springforce being adjustable by means of a knob 478. Relative rocking movementbetween the feeler member and the arm when an ear is engaged is utilizedto control a switch 480 as will be covered in conneciton with adiscussion of the control diagram, FIG. 21.

For the purpose of rocking the arm forwardly to place the feeler memberin the path of upward movement of the pail, a cam 481 is provided on theshaft engaged by a cam follower 482 which is pinned to the lower end ofthe carrier portion 474 of the arm. Thus, in a typical sequence it willbe understood that the arm is rocked radially inward toward the pail sothat the tip 473 is in the path of movement of the ear. Continued11pward movement of the pail by the positioning member causes the springto be compressed, with rocking movement of the feeler member 472accompanied by actuation of the switch 480. The pressure exerted by thespring 477 is sufiicient so that there is insurance that any ear whichpasses the checking step will have a strength which is adequate for allnormal usage of the resulting pail although the checking mechanism doesnot develop the full strength of the weld.

In order to hold the pail steady as it is acted upon by the feeler arms,a disc 490 is provided which is similar to that in the welding station.The disc is carried on a vertical shaft 491 slidably received in abushing 492 and urged in a downward direction by a coil spring 493.

The last station 66 is an idle station which may be employed to performan added operation on the pails thereby to increase the versatility ofthe machine. It includes a clamping disc 500 on a shaft 501 slidable ina bushing 502 and with the disc being biased downwardly by a spring 503.When the pail leaves the station 66 it is moved by the transfer memberonto the conveyor 150. A reciprocating type pusher mechanism may beemployed to move pails laterally from the conveyor for reject purposes.

In the above discussion, it has been assumed that the mechanism has beenadjusted for one size of pail. Means are provided for accommodating themachine to pails of different heights by raising or lowering thesuperstructure 55. Conveniently, this may be accomplished by a heightadjusting drive including a motor 510 having an angular drive connection511 for rotating shafts 512., 513 which extend along the top of themachine. Such shafts rotate worm driven nuts 514, 515 which cooperatewith threaded jack screws 516, 517. It will be apparent, then, thatsimply rotating the motor in one direction or the other thesuperstructure may be moved upwardly and downwardly along way surfaces.As previously disclosed this does not effect the adjustment of therotary orienting mechanism because of the double parallelogram linkageemployed in the latter.

Integrated control circuit While the sequence of operation of thewelding machine will be understood in the general way from the precedingdiscussion of the structure, it is one of the features of the presentinvention that the various functions are integrated in a novel fashionunder the control of a control circuit which is set forth in simplifiedform in FIG. 21. To insure proper timing of the various functions weprefer to use a multiple section cam switch which is coupled to the camshaft 83 at a 1:1 speed ratio. The cam switch is indicated generally inFIG. 2 by the numeral 530 and it may be conveniently driven by asuitable angular drive connection from the same chain 143 which servesto drive the conveyor 140. The various sections of the cam switch havebeen indicated in FIG. 21 at 531-539 inclusive.

Turning to FIG. 21, lines 551, 552 will be understood to be connected tothe regular commercial supply line. In series with the main drive motor90 is a switch or control 553. In series with the orienting motor 181 isa suitable switch 554. The motor 555 which drives the hoppers has acontrol switch 556. Finally, the adjusting motor 510 for adjustingheight of the structure, which is of the reversible type, has up anddown switches 557, 558.

It will be understood that during the normal operation, control switches553, 554 and 556 will be closed and the switches 557, 558 will be openso that the adjusting motor remains at a constant adjustment.

As the cam shaft 83 rotates to drive the transfer and positioningmembers 70, 100, pails will be transferred simultaneously into all ofthe stations. Directing attention to the pail in the first orientingstation 61, the sections 531, 532 of the cam switch are closed, therebyclosing the circuit to a course orient relay 560 having contacts 561,562, 563. The contacts 561 are normally open and connected in serieswith the clutch 175 While the contacts 562 are normally closed andconnected in series with the brake 176. The contacts 563 which arenormally open, serve the purpose of sealing in contacts and areconnected in series with the switch 194 controlled by the star wheel190. Because of the scaling in contacts, the relay 560 remains closed,energizing the clutch 175 to rotate the pail engaged by the disc 170.When the seam of the pail arrives, tripping the star wheel 190, theswitch 194 momentarily opens, dropping out the relay. This deenergizesthe clutch so that the seal is stopped with the seam thereonapproximately oriented in desired position.

Directing attention next to the pail in the fine orient station 62,there is provided a relay 570 having contacts 571, 572 and 573. Theswitch 255 of the detector 250 is connected in series with the contacts573 which perform a scaling function. After a pail has been moved intothe orienting station 62, the section 533 of the cam switch is closed,picking up the relay 570 and energizing the clutch 175a. This producesrotation of the disc 170a at slow speed because of the step-down geardrive shown in FIG. 8. When the slow speed detector engages the seam ofthe pail, the switch 255 is opened dropping out the relay 570 whichdeclutches the drive and energizes the brake 1761) to locate the pail ina precisely oriented position.

For the purpose of dropping cars into the welding station, theescapement 310 shown in FIG. 6' is, as stated, operated by two solenoids314, 314a under the control of the sections 534, 535 of the cam switch.The timing of the cam switches is such that the two solenoids arenormally operated in sequence. Thus, the solenoid 314 will be operatedto drop an ear, but before the next car can be dropped the escapementmust be reset by operating the reload solenoid 314a. In accordance withone of the detailed features of the invention, the overtravel switch256, which is under the control of the slow speed detector 250, isconnected in series with the reload solenoid 314a. Consequently, thereload solenoid performs a memory function, i.e., no reloading of theescapement takes place to enable dropping of an ear in the succeedingcycle. To summarize, any overtravel of the pail in the final orientingstation opens the switch 256 to prevent reloading of the escapement;consequently, when the mis-oriented pail reaches the next, or weldingstation, no ears will be dropped on either side of the pail forengagement by the gauge pins 331 to enable operation of the weldcontroller. The weld controller has been indicated at 580.

Turning attention to the weld controller circuit, it will be noted thatthe switches 458, which are normally closed, and the switches 457, whichare normally open, associated with the gauge pins 331, are all connectedin series with the section 536 of the cam switch. Thus, the cam switch,when the remainder of the circuit is completed, normally acts toenergize the weld controller 580 to initiate the welding. The nature ofthe weld controller, and the particular sequence of force and currentwhich is employed in the present invention will be covered in thefollowing section.

However, in the illustrative apparatus and as far as the gauge pinswitches are concerned, the absence of any ears in the welding stationcauses the pins to overtravel, thereby opening the normally closedswitches 458 and reventing a circuit from being completed to the weldcontroller. In short, when no ear-drop takes place to a mis-orientedpail, the weld controller is effectively disabled so that no weldoccurs.

In the illustrative apparatus, means are provided for countingsuccessive pails found to lack ears in the check ing station and forshutting down the machine, or for notifying the machine operator, whenthe number of such successive pails reaches a predetermined total. Itwill be understood from the above that the lack of ears on a pail in thechecking station will most commonly be due to the fact that such pailwas not properly oriented thereby disabling ear-drop reload solenoid314a. Thus, it is presumed that when a group of successive pails arefound to be without ears, the machine should be shut down untilappropriate adjustment may be made in the final orienting station. Toaccomplish automatic shut down there is provided in the present devicean ear test relay 585 having normally open contacts 586 and normallyclosed contacts 587. The relay 585 is connected in series with section537 of the cam switch and the ear test switches 480 in the ear checkingstation at opposite sides of the machine. The contacts 586, 587 are usedto control a counter 590 having a count line 591 and reset line 592.Connected in series with the reset line is section 538 of the camswitch.

The ear checking switches 480 are normally closed. Thus, in the eventthat a pail in the checking station lacks ears, switches 480 will remainclosed with the re sult that cycling of the cam switch section 537applies an impulse to the relay 585, picking up the relay to causeclosure of the normally open contacts 586 to register a count in thecounting circuit. To store the count, i.e., to prevent resetting of acounter upon do energization of the relay 585, a latching relay 595- isemployed having a latch 596 which engages a cooperating latch member 597on the plunger of the relay 585. Thus, the relay 585 is, temporarily,prevented from dropping out to the point of closing the contact 587.

If the next pail to enter the checking station 65 is also 15 withoutears, the above operation will be repeated, i.e., the relay 585 will beenergized to close the contacts 586, so that a second count isregistered in the counter. The counter may be a commercially availabledesign so that upon reaching a set count, output contacts are operated.The output contacts, in the present instance indicated at 598, are inthe form of normally closed contacts connected in series with thecontrol circuit for the main motor 90. Thus, when the desired count ofnon-eared pails is reached, which may be five in a practical case, themain driving motor is shut off, bringing the machine to a halt andclearly signifying to the operator that an adjustment should be madebefore operation is continued.

However, when an eared pail is detected prior to the set count,resetting is effected by section 539 of the cam switch. Since the latteris in series with the latch relay 595, the latch 596 is withdrawn andcontacts 587 are closed to apply a reset signal to the line 592 whichfeeds the counter.

In order to prevent the latching relay from producing unwanted reset,the on time of the cam section 539 is made very short and is adjusted tofall within the on time of the cam section 537. Thus, when a pailwithout ears is in the checking station, resulting in energization ofthe rely 585, the latching relay 595 will be momentarily energizedduring the time interval that the relay 585 is picked up. Because of theshortness of the time of energization of the latching relay, the latchwill fall back into latching position before the relay 585 becomesdeenergized. Briefly stated, while it is true that the latching relay595 is operated once each cycle, it is effective to unlatch the relay585, i.e., to permit it to drop out, only when there is an cared pail inthe checking station, since it is only then that the switches 480 areopened.

While the construction and operation of the counter 590 will be apparentto one skilled in the art from the foregoing description, it will "beunderstood that we prefor to employ a counter of type HZ 150A60lmanufactured by Eagle Signal Co. and described in their Bulletin 725.

For the details of the program of the cam switch, reference is made toFIG. 21a which shows the on time for the switch sections 531-539employed in the case of a practical installation.

Force-current cycle of projection welding through protective coatingWhile the discussion has been directed toward the structural aspects ofthe welding machine, it is one of the important features of theexemplary apparatus and welding system to provide a specificrelationship between the structure and the specific force-current cyclewhich has been found to enable perfectly reliable welding through paint,lithographing, or other protective coating on the surface of the pail.As stated above, it is contemplated that the painting or lithographingwill take place while the pail is still in the fiat condition, with thesurface being thoroughly covered so that no bare spots are available formaking electrical contact.

We preferably employ a projection which is the result of a piercingoperation so as to produce a tapered relatively sharp edge of limitedcross section. A sectional view, taken through the projection andassociated base member (the wall of the pail) is set forth in FIG. 23a,the scale being greatly enlarged to facilitate understanding. Thus, theprojection indicated at 600, has a relatively sharp edge 601. In apractical case, such edge will not be smooth and continuous but on thecontrary will be ragged or sawtoothed to define a number of projectingpoints arranged in a circular locus. In the same figure the base memberhas been indicated at 605 and the coating thereon by the layer 606. Theprojection has a height from the surface of the attachment indicated athl. The welding electrodes 369, 371 previously discussed, and which areindicated by the dimension line in the figure preferably occupy an areawhich is substantially greater than the diameter of the projection, themajor diameter of the projection being indicated at d1 and the minordiameter at d2.

In order to better understand the reasons for the effectiveness of thepresent apparatus and procedure in securing a sound Weld through aninsulating coating a series of stop motion cross section views have beenprepared as set forth in FIGS. 23a-23b inclusive and which are keyed toa plot of projection height, pressure and current in a typical weldingcycle. The figures are based upon actual observations made in an effortto explain successive occurrences during the cycle.

FIG. 23a shows the initial condition with the electrodes brought intolight contact with the work but with substantially zero force appliedand with the coating not yet penetrated. Upon slight additional movementof the movable electrode, the force applied rises rapidly as indicatedat F1. Since the spring is preferably stiff having a pre-stress force ofapproximatelly 330 pounds, concentrated upon a projection diameter d2 ofonly 0.040 inch, the sharp edge of the projection is forced through thecoating to establish a limited area of electrical contact followedimmediately by deformation or partial axial collapse of the projectionto the condition shown in FIG. 23b and with the projection height beingreduced to a value I22. That is, the sharp edge 601 is crushed and tendsto spread out in both radial directions, defining a reduced innerdiameter d3 and an increased outer diameter a'4. The net effect is tosubstantially increase the cross sectional area of the metal at the edgeof the projection. The initial electrical contact made between theparts, for example, as indicated at 607, is maintained during thetransition and, in the following steps, the areas of electrical contactmay even be enlarged depending upon the nature of the coating material.It may be emphasized at this point that advancement of the electrode 369and the build-up of force along the applied force curve takes placepositively substantially free of the effect of inertia or othertransient effects which characterize air actuators or the like commonlyemployed in welding practice. Thus, the transition between conditions ofcontact shown in the stop motion views is progressive from the time thatthe initial electrical contact is made to the time that the projectionis substantially flattened and free of any momenary release or reboundwhich might affect the continuity of the electric circuit.

As the spring 380 in the welding gun 351 is picked up, in other words,as the central rod 358 is unseated from the seat 382 in the gun, theforce exerted by the electrode 369 further increases, reaching a valueF2 (FIG. 22) accompanied by further deformation of the projection, withthe height being reduced to the value b3, the inner diameter beingreduced to the value d5 and the outer diameter being increased to thevalue :16. The contact areas 607 remain in engagement and some of thecoating material is trapped as indicated at 608.

At the end of the forward stroke of the gun actuating bar 398 (FIG. 14),the throw of which is determined by the cams which drive it, the .barremains temporarily stationary to apply a high sustained force to thewelding electrode having a value indicated at F3 in FIG. 22. Increase inforce to the maximum value further deforms the projection until itappears as set forth in FIG. 23d. Here it will be noted that the innerdiameter of the projection has been reduced to the point where theprojection is substantially closed. The contact is maintained andenlarged over areas 607 and pockets of coating material 608 become morewell-defined.

Application of full welding current is delayed until after theprojection has been substantially deformed, that is, substantiallyflattened out as indicated in FIG. 230 or FIG. 23d. Thus the current ispreferably turned on at point c1, i.e., after a delay time t1 from thestart of the welding cycle which may be in the order of & second. Thistiming is achieved in the present instance, by the phase of section 536of the cam switch is in series with the input to the welding controller.However, as the discussion proceeds it will be apparent to one skilledin the art that such delay need not be secured by a timed switch andthat, if desired, the current may be initiated by a switch which isresponsive to the build-up of the force applied by the electrode 369 andspring 380.

The current, when applied, is not applied at full welding value butmeans are provided within the welding controller 580 for causing thecurrent to build up from a reduced value c1 or less linearly along acharacteristic curve 02 to a final value 03. Such build up of current ina practical case may take place over an interval t2 on the order of Asecond in length. Welding controllers capable of such upslope withvariable rise time are commercially available.

Current and force are both thereafter maintained at the values 03, F3,respectively, which may be in the order of 9000 amperes and 350 pounds,over a further interval t3 which may be on the order of 0.25 second. Theheating which takes place during this time interval produces atemperature which is sufficiently high so that the metal softens andflows under the applied pressure so that complete flattening of theprojection takes place, with loss of identity and with the two pieces ofmetal being united over the area of a welding nugget 610 having an areawhich is substantially greater than the area of the original projection.During this portion of the cycle any entrained coating material isdecomposed and is found not to affect the soundness of the weld.

It is found that by using the above procedure, flashing, i.e., theburning away of the projection, is completely eliminated and that eachweld is sound and homogeneous notwithstanding the insulating paint orother coating. Observations show that the elimination of flashing is duein part to the deformation of the thin tapering edge of the projectionfrom the thin initial cross section to substantially thicker crosssection before the application of current without interrupting thecontinuity of the contact originally made and with substantial increasein the thermal coupling between the projection and the relativelymassive pieces of metal lying on the opposite sides of the projection.Because of the increase in cross section and the close thermal couplingexcess localized heat is promptly conducted away so that there is nopossibility of temperature build-up in the projection to the level atwhich burning or flashing away may occur. Localized build-up of heat inthe projection is also minimized by the fact that the electrodes, bothmovable and fixed, constitute an efficient heat sink.

The continuous maintenance of electrical contact from the moment ofinitial contact by the points of the projection is also believed to be acontributing factor. As stated, such contact is maintained by reason ofthe fact that the electrodes are advanced positively and progressivelywithout being affected by inertia etfects or rebound. Moreover, use of apierced projection tends to produce a scraping action as the projectionis deformed, with part of the edge scraping inwardly to reduce a minimumdiameter of the projection and the remainder scraping outwardly toincrease the maximum diameter. Where such a projection is used and wherethe parts are put through a pressure cycle without application of thewelding current, it is found that the insulating coating tends to besubstantially cleared from a small but rather well defined annular area.This scraping action is, however, to be distinguished from the scrapingwhich might occur due to bodily deformation of the car being attached.In the present procedure deformation is limited to the projectionitself.

After the welding current has been applied the additional time t3 thecurrent is cut off as shown in FIG. 21 but force continues to be appliedfor an additional time interal t4 to permit the weld to cool and remainintact when the force on the welding electrodes is released.

It is particularly noteworthy that all of the above occurs within anextremely short period of time, on the order of one-half second and itis, indeed, one of the features of the present machine that in spite ofthe sequential action production rates are obtainable which arecomparable to or even higher than where conventional bare metal weldingtechniques are employed.

While a pierced projection has been described as the preferredembodiment, it will be understood that other specific shapes ofprojections may be employed having a relatively sharp edge forpenetrating a coating, where the edge is either continuous or localizedin the form of a point and where deformation of the edge occurs toincrease the cross section and hence the thermal coupling uponapplication of force and prior to the application of the full weldingcurrent.

It will also be understood that there has herein been described andillustrated a novel apparatus and method for insuring that cars(attachments) are welded only to those pails (base members) which areaccurately positioned in the welding station in a predetermined orientedposition. Thus, to the extent that a given pail exceeds the positionaltolerance defined by the switches 255, 256 the normally closed switch256 will open, thereby creating a control signal in the form of theabsence of the preset potential or signal level required to engagesolenoid 314a. However, it is also within the scope of the invention tomake use of a normally open switch (not shown) which is closed when thepositional tolerance is exceeded, in which event the control signalmight take the form of the presence of a preset potential or signallevel which is effective to prevent energization of either the earfeeding circuit or the welding circuit. Thus, those skilled in the artwill appreciate that the control signal may take the form of either thepresence or absence of a predetermined signal level and, it can becreated either by detection of a misoriented pail-in which event it willserve to disable the ear-feed mechanism and/ or the weld circuitor bydetection of a properly oriented pail-in which event it will serve toenable the ear-feed mechanism and/ or the weld circuit.

We claim as our invention:

1. In a welding machine for welding an attachment to a base member, thecombination comprising a machine frame, means for supporting a basemember on said frame in a predetermined orientation relative thereto,means for feeding an attachment relative to the base member to positionthe attachment adjacent the base member, means for sensing the positionof the base member relative to said frame to detect oriented andmisoriented conditions thereof, means responsive to said sensing meansfor disabling said feeding means upon detection of a misorientedcondition of the base member relative to said frame, and means forwelding to the base member attachments which are fed by said feedingmeans.

2. The combination as set forth in claim 1 further characterized in thatsaid feeding means includes an escapement, said escapement having meansfor accepting and discharging attachments fed thereto one at a time.

3. The combination as set forth in claim 2 further characterized in thatsaid escapement is disabled upon detection by said sensing means of amisoriented condition of the base member relative to said frame.

4. In a system for welding attachments to base members, the methodcomprising the steps of:

(a) orienting the base member relative to a reference point;

(b) sensing the position of the base member relative to the referencepoint;

(e) creating a control signal indicative of the particular sensedposition of the base member relative to the reference point;

(d) feeding an attachment to a position adjacent to and in contact withthe base member;

(e) welding those attachments which are fed to positions adjacent to andin contact with accurately oriented base members to such base members;and

(f) utilizing the control signal created during step (c) to prevent thecarrying out of steps (d) and (e) when a condition of misorientation ofthe base member relative to the reference point is detected.

5. The method as set forth in claim 4 further characterized in that thebase members are pails and the attachments are ears.

6. In a system for welding attachments to base members, the methodcomprising the steps of:

(a) orienting the base member relative to a reference point;

(b) sensing the position of the base member relative to the referencepoint;

(e) feeding at least one attachment to a position adjacent to and incontact with the base member;

(d) disabling the feeding means whenever the sensing means detects amisoriented condition of the base member relative to the referencepoint; and,

(e) welding those attachments which are fed to positions adjacent to andin contact with base members to the base members in their orientedpositions.

7. In a system for welding attachments to base members, the methodcomprising the steps of:

(a) orienting the base member relative to a reference point;

(b) sensing the position of the base member relative to the referencepoint;

() creating a control signal indicative of the particular sensedposition of the base member relative to the reference point;

((1) feeding an attachment to a position adjacent to and in contact withthe base member;

(e) welding those attachments which are fed to positions adjacent to andin contact with accurately oriented base members to such base members;and

(f) utilizing the control signal created during step (c) to prevent thecarrying out of step (d) when a condition of misorientation of the basemember relative to the reference point is detected.

8. In a system for welding attachments to base members, the methodcomprising the steps of:

(a) orienting the base member relative to a reference point;

(b) sensing the position of the base member relative to the referencepoint;

(c) creating a control signal indicative of the particular sensedposition of the base member relative to the reference point;

(d) feeding an attachment to a position adjacent to and in contact withthe base member;

(e) welding those attachments which are fed to positions adjacent to andin contact with accurately oriented base members to such base members;and

(f) utilizing the control signal created during step (c) to prevent thecarrying out of step (e) when a condition of misorientation of the basemember relative to the reference point is detected.

References Cited UNITED STATES PATENTS 2,394,599 2/1946 Edelman et al.219-79 2,748,235 5/1956 Wallace 219-78 2,912,563 11/1959 Schlieker et al2l978 RICHARD M. WOOD, Primary Examiner.

BARRY A. STEIN, Assistant Examiner.

11.8. C1. X.R.

